When US-based discount website Groupon launched a unique life-changing competition, Josh Stevens told his girlfriend he'd have no chance of winning. Live Off Groupon would clearly attract thousands of applicants because the winner would get to travel the US for a year using only Groupon vouchers plus $100,000 (£61,100) in cash at the end of it. Why would it pick an unemployed ex-accountant from Chicago?

He had sent in a video application, in which he demonstrated an array of silly, but creative, uses for the vouchers (fending off a bear attack using voucher-blowdarts and fashioning a parachute out of Groupons, for example). But he never thought he would get anywhere.

Fast-forward to April 2011 and Stevens, 28, is in London on his first ever overseas trip, enjoying his first full English breakfast and nearing the end of his Groupon-funded year of travel. It has taken in 40 cities across the US, as well as this hop across the pond. He has just 34 days to go until he receives his cheque back in Chicago, site of Groupon's head office.

He embarked on his journey wearing only a paper suit made from the vouchers, a pair of shoes, one pair of socks and one set of underwear. "The first thing I did was to get a horse and carriage into town and buy some more clothes."

Stevens has also been documenting his progress (he was given a camera, video camera and iPhone) on a blog liveoffgroupon.com, Facebook and Twitter – the discount company is nothing if not plugged into the social networks.

Groupon has been phenomenally successful at using collective buying to offer discounts off local goods and services – it claims to have saved subscribers $2bn since it launched in November 2008 and, in the UK alone, has attracted eight million subscribers in one year.

Coupons are officially big business. In the US there is even a show called Extreme Couponing on the TLC channel where fans can detail how much they are saving. But many say the vouchers have become a necessity. As one person on the forums wrote: "TLC is missing the real stories of real couponers. What about the ones who are doing it to survive? Husbands laid off, hours cut back, couponing so they can keep their home."

With that in mind, some may view Groupon's expensive and extended publicity stunt (Stevens's first assignment was an appearance on the US Today show) as distasteful. It operates towards the luxury end of the market (offering discounts on beauty treatments and hotel accommodation, rather than supermarket-style coupons), which begs the question of how it is possible to live off the vouchers.

Stevens says only by trading them and relying on the kindness of strangers. He has also learned never to pay for the internet, use free refills, use Skype instead of paying for calls, enjoy free events and load up on hotel freebies. "Groupon vouchers do not work everywhere. Often they only work for businesses in central areas of a city, so if you find yourself in the suburbs you can get stuck," he explains. "I probably managed to use vouchers for about 20% of my accommodation, the rest was couch-surfing or staying with friends of friends." He has never had to sleep rough, but has stayed on people's floors – he quickly acquired a blow-up airbed.

The competition rules meant that Stevens could only stay with people he knew for two nights per month, meaning he has met a lot of people en route with whom to trade vouchers in return for meals, massages or motels. "I've already traded some in London for an Oyster card," he grins.

Friendly locals have made him packed lunches and offered food – a bonus given Stevens is 6ft 6ins and requires a lot of fuel. "I've also discovered some weird food," he says, tucking into black pudding for the first time in his life, "including sea urchins and mako shark."

"The best night of the trip, so far, was at the Fairmont Heritage Place hotel in San Francisco," he says, "where I had a $600 (£368) a night, two-bedroom apartment. I could have held a cocktail party for 30, it was so big." Fairmont Hotels & Resorts is, naturally, a sponsor.

Stevens did not make it all the way from Chicago to Heathrow using a voucher. "Groupon paid," he admits. "I wanted to pay for it myself. I could have asked people to contribute and got enough to buy a flight, but the logistics made it too complicated."

Stevens is referred to as a "Groupawn" by the company, but has he had to sell his soul to it in return? "It has pretty much left me to myself," he explains. "There was a lot of contact in the beginning, not so much in the middle, and it's getting a little busier towards the end."

Loneliness, or boredom, have not been a problem. He has been set challenges en route (in London he has to pretend to be British in a bar, and run from one end of Tower Bridge to the other) while the constant bartering and trading means he is forever in others' company.

"I never get to switch off. I'm always a guest and always talking to people, so it's hard to relax. It's been a very long time on the road. But I have no regrets."

Then there's the small matter of that $100,000. "After tax and paying off my student loans, there will be a nice little nest egg," he says.

• Correction: This article was changed at 10:40 on 11 April 2011. It originally converted $100,000 into £614,000. This has been changed.